Central Asia: Western China

This xeric ecoregion, located between China’s Kunlun and Tian Shan Mountains, is the largest desert in China. The world’s largest shifting-sand desert, eighty-five percent of this ecoregion consists of sand dunes that support very little or no vegetation. There is little biodiversity in such a harsh environment, yet such mammals as the wild Bactrian camel (Camelus ferus) and Asian wild ass (Equus hemionus) manage to persist. Unusable as farmland for humans, the Taklimakan desert remains very much intact, although a history of nuclear testing in Lop Nor represents a considerable threat.

Scientific Code

(PA1330)

Ecoregion Category

Palearctic

Size

286,400 square miles

Status

Critical/Endangered

Habitats

Description Location and General DescriptionThe Taklimakan is China’s largest, driest, and warmest desert. It fills the expansive Tarim Basin between the Kunlun Mountains and the Tibet Plateau to the south and the Tian Shan (Celestial Mountains) to the north. Located farther from the ocean than almost any place on Earth, this region is completely cut off from the effects of the Asian monsoon. Arctic storms from the north are also blocked by the encircling mountains. Because the basin lacks drainage, salt has accumulated over large areas. The Taklimakan is also known as one of the world’s largest shifting-sand deserts. Fully 85 percent of the total area consists of mobile, crescent-shaped sand dunes that may reach a height of 100 to 200 m and are virtually devoid of vegetation.

On the alluvial fans that spread outward from the foot of the mountains to the floor of the basin, perennial freshwater springs are fed by mountain snowmelt. The Tarim River also flows across the basin from west-to-east. In these places, the oases created by fresh surface water support a distinct ecoregion, the Tarim Basin Deciduous Forest.

According to MacKinnon et al. (1996), a transect through the Tarim Basin from high mountain slopes to the edge of the desert reveals a distinctive sequence of landforms. Higher on the slopes, exposed surfaces are denudational: they are sculpted by the removal of material through wind and water erosion. Basin landscapes are depositional: they consist of gravel, sand, silt or clay, depending on the velocity of the water transporting material to the site. The floor of the basin includes large expanses of water or wind-deposited sand. Toward the margin, this sand is fixed and stable. Closer to the middle, it consists of unconsolidated, shifting dunes. Among the dunes are areas of salt marsh and salt flats that may be sporadically inundated. The lowest point in the Tarim Basin is 154 m below sea level.

Diurnal and seasonal temperature variations are both severe in this arid, continental basin. Day and night temperatures may differ by 20oC. Winter-summer temperatures may differ by 30oC. The overall climate, however, is warmer here than the other desert regions of China due to lower latitude and low elevation. In the center of the basin, precipitation is scant: less than 10 mm per year. But this increases to about 100 mm per year at the foot of the mountains and may reach 400 to 800 mm per year on the upper slopes above 3,000 m elevation which are high enough to intercept arctic storms during winter. The presence of an adequate snowpack in the high mountains explains the large oases in the basin. These once supported deciduous poplar forest, but today they have been converted to irrigated agriculture.

Most of the Tarim Basin, including the Taklimakan Desert, consists of shifting sand with virtually no vegetation. When sand movement slows, dunes may be colonized by such plant species as Alhagi sparsifolia, Scorzonera divaricata, and Karelina caspica. Peripheral areas consist of more stable gravel substrates where vegetation cover may approach 5 percent. Dominant plant species here include the shrubs Ephedra przewalskii and Nitraria sphaerocarpus, although today the vegetation of the Tarim Basin is extremely depauperate. The northern margin of the Taklimakan Desert, and areas at the periphery of the Tarim River riparian zone, support steppe vegetation dominated by saxaul (Haloxylon spp.) together with other salt-tolerant shrubs.

Biodiversity FeaturesPartly because it is so inhospitable to humans, the Taklimakan Desert continues to support small populations of animals like wild Bactrian camels (Camelus ferus) and Asian wild asses (Equus hemionus) that have been extirpated in other parts of China.

All of the 500 Bactrian camels that survive in the wild in China inhabit the Taklimakan, mostly in the area to the east of the (now dry) Lop Nor Lake. Arjin Shan Wild Camel Nature Reserve (15,125 km2) has been mapped to conserve habitat for this species, but the wild camels are still thought to be in a state of decline. An extension of Arjin Shan Nature Reserve is located at higher elevation in the basins of the Kunlun Mountains to the south. If these two large protected areas are managed successfully, they will be valuable for desert conservation in China. A roughly equal number of wild Bactrian camels occur in Great Gobi National Park in Mongolia.

Current StatusResource problems include the history of nuclear testing in Lop Nor and declining air quality as wind blows dust from lakes that have become dry due to irrigation. On April 15th, 1998, a dust storm in western China produced a huge atmospheric dust cloud that was transported across the Pacific Ocean and caused elevated aerosol concentrations 10 days later over the Pacific Coast of North America.

Types and Severity of ThreatsFurther population increases due to translocation of people from eastern China threatens the existing oases because this water is used to expand crop irrigation.

The wild camel gene pool could be threatened by interbreeding with domestic camels which are abundant in many areas of the Tarim Basin. Strategies to promote gene flow between the Chinese and Mongolian wild camel populations could be pursued if, in fact, these populations had interbred in recent historic time.

Justification of Ecoregion DelineationThe ecoregion boundary is based on the CVMCC (1979) Vegetation Map of China classes desert steppe (47), shrubby and rocky desert (52, 57, 59, 60a) with sand dunes, saline soil, and sparsely vegetated areas as dominant land cover. This is comparable to the Tarim Basin biogeographic subunit in the Takla-Makan-Gobi Desert according to Mackinnon et al. (1996).